3 Questions for you, please (I understand these may need to go to Engineering):

Is there any information available regarding storage limits on Intuit's cloud server per subscription of QBO?

Are newly created companies receiving different database resources, reporting infrastructure, or post-copy optimization than legacy or established companies?

If, after researching the below, I need to pose a question directly for investigation per use case - unless you tell me differently, I suppose I might ask something like:

"Please investigate whether a copied company’s reporting indexes, post-copy database processing, tenant provisioning, or report-service allocations are completing correctly?" - OR if I need to provide specific use-cases for investigation.

The context:

I have several clients who were either in regular retail subscriptions of QBO obtained directly through Intuit or wholesale subscriptions provided by their ProAdvisor who migrated using Intuit's Backup + Restore (Copy) feature, and the reports take FOREVER to load to in the new subscription.

There is also no consistent rhyme or reason (which browser, date of the move, length of historical data, subscription tier(s), or when the attempt to run the report was made as it happens when checking over several days), and since the original data file has exactly as much information as the new one - this leads me to believe it is either a server limitation placed on newer subscriptions OR some type of indexing, cache, or optimizations limitations regarding databases or reports failing on newer subscriptions since it does not happen in the originals.